About 60% of natural conceptions fail to implant properly. One of the reasons may be the failure of the embryo to generate Trypsin, a chemical which induces a receptive environment in the uterus in order for the fetus to be implanted. The excess or lack of chromosomes of the fertilized egg may also be a factor in implantation failure. A weak immune system of the woman may also be an important factor.
D.
The temperature won't make a difference since neither mass nor energy can be created or destroyed.
No they are not the opposite, they are the end products for photosynthesis.
I believe the answer is protein synthesis.
